1. Field of the Invention
The invention relates to bags or packs and, more particularly, to backpacks.
2. Description of Background and Relevant Information
Backpacks typically comprise a pack portion, usually made of relatively flexible (i.e., non-rigid) materials such as panels of textile fabrics, which forms a compartment adapted to receive a load to be carried. The pack portion comprises a back side which is positioned opposite the back of the user when it is worn. The backpack also has a carrying system which can comprise a pair of shoulder straps and possibly a hip-belt.
Being made of flexible materials, a loaded backpack tends to deform due to the volume and/or the weight of the load inside the pack. In particular, the back side can deform, which is most uncomfortable to the user.
In order to prevent such unwanted deformation, at least partly, it is known to provide the backpack with a stiffening frame along its back side. Such frames may be of different kinds. Some packs are equipped with one or more rigid rods (or stays) which are inserted in gussets attached to the back side. These rods are usually made of metal, plastic, or composite material, and they run substantially vertically along the back side. Other packs have a frame made of a sheet of semi-rigid or rigid material which is inserted in a gusset pocket of corresponding shape attached to the back side (usually on the inner side of the back side). Such sheet frame can be made of various materials, including plastic, composite materials, or rigid or semi-rigid foams. In the latter case, it can be provided that the sheet frame of semi-rigid foam is made of a folded sheet which is removably inserted in the gusset pocket and which can be removed to be used as a sleeping mattress for outdoor sports enthusiasts.
A sheet frame can also be reinforced by removable or non-removable rigid rods, and it can also be complemented by a layer of soft foam to provide additional carrying comfort for the user.
In most backpacks having a hip-belt, the carrying system is made to shift at least part of the weight of the load off the shoulder straps, down to the hip-belt, in order that at least part of the weight of the load is carried by the hips of the user rather than having his/her shoulders and back carry all the load. The stiffening frame participates in that load transfer by making a link between the shoulder strap attachment portions of the pack portion and its hip-belt attachment portions.
Nevertheless, conventional backpacks having a stiffening frame share in common that the frame is not an integral part of the pack and that this introduces undesirable movements and deformations between the frame and the relatively flexible material of the back side.
U.S. Pat. No. 4,750,654 discloses a backpack in which the flexible pack portion has no back side, the back side being made of layered structure comprising two layers of cellular synthetic resins (i.e., foams) over-molded on a fabric layer. The flexible pack portion is sewn onto the outer periphery of the back side structure.
Another problem with prior art backpacks is that most of them are not waterproof, not even water resistant. Waterproof bags are known in the art, such bags typically made of PVC-coated materials. Such waterproof bags are made by assembling panels by welding.
Welding is here opposed to gluing. Gluing requires the provision of an adhesive material between the two pieces to be assembled, whereas welding means that the surface of at least one of the pieces to be assembled (but preferably both) is melted to adhesively bond the two pieces. Both welding and gluing result in an adhesive bonding of the two pieces.
Welding operations are quite complicated as they require the use of complicated tools to press and heat the panels to be assembled along the necessary junction line. Such tools are even more complicated when it comes to welding along a non-straight line, and even worse when the junction line is three dimensional. On such PVC-coated bags, various handles and straps may be connected to the exterior surface of the bag. The technique used up to now has been to provide anchoring pads of plastic material, on which the handle or the strap is affixed, for example by sewing, and to weld the pads to the outer surface of the material.
Unfortunately, in some cases, the welding operation only permits welding along the periphery of the pad, not along its entire contacting surface. This is due to the presence of the strap or handle which is affixed to the pad, usually in the center of the pads, and which therefore makes it difficult to bring enough heat and pressure to the center of the pad to achieve welding.
Moreover, those bags have the undesirable feature of requiring PVC-coated or urethane-coated materials when it is now known that extensive use of PVC is undesirable in view of environmental issues. At least for this reason, urethane-coated waterproof bags are known in the prior art.